U.S. patent application number 16/445901 was filed with the patent office on 2020-02-13 for power transmission device for vehicle.
This patent application is currently assigned to EXEDY Corporation. The applicant listed for this patent is EXEDY Corporation. Invention is credited to Yoshihiro MATSUOKA.
Application Number | 20200047611 16/445901 |
Document ID | / |
Family ID | 67262140 |
Filed Date | 2020-02-13 |
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United States Patent
Application |
20200047611 |
Kind Code |
A1 |
MATSUOKA; Yoshihiro |
February 13, 2020 |
POWER TRANSMISSION DEVICE FOR VEHICLE
Abstract
A power transmission device includes an electric motor, and a
torque converter connected to the electric motor to transmit
torque. A torque converter characteristic line is determined based
on a capacity coefficient of the torque converter and indicates
torque of the torque converter relative to each rotational speed of
the torque converter. An electric motor characteristic line
indicates a maximum output torque of the electric motor relative to
each rotational speed of the electric motor. A first range
corresponds to a range equal to and greater than a base rotational
speed of the electric motor and equal to or less than a first
average rotational speed, which is an average of the base
rotational speed and a maximum rotational speed of the electric
motor. The capacity coefficient is such that the characteristic
line for the torque converter intersects the characteristic line
for the electric motor in the first range.
Inventors: |
MATSUOKA; Yoshihiro; (Osaka,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EXEDY Corporation |
Osaka |
|
JP |
|
|
Assignee: |
EXEDY Corporation
|
Family ID: |
67262140 |
Appl. No.: |
16/445901 |
Filed: |
June 19, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L 2240/423 20130101;
B60K 1/00 20130101; H02K 1/27 20130101; B60L 15/20 20130101; B60W
2710/083 20130101; F16H 41/24 20130101; B60K 17/02 20130101 |
International
Class: |
B60K 17/02 20060101
B60K017/02; F16H 41/24 20060101 F16H041/24; B60K 1/00 20060101
B60K001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2018 |
JP |
2018-148812 |
May 7, 2019 |
JP |
2019-087750 |
Claims
1. A power transmission device for a vehicle, comprising: an
electric motor; and a torque converter connected to the electric
motor and configured to transmit torque of the electric motor to an
output member, wherein a characteristic line for the torque
converter is determined based on a capacity coefficient of the
torque converter and indicates torque of the torque converter
relative to each rotational speed of the torque converter, a
characteristic line for the electric motor indicates a maximum
output torque of the electric motor relative to each rotational
speed of the electric motor, a first range corresponds to a range
that is equal to and greater than a base rotational speed of the
electric motor and is equal to or less than a first average
rotational speed, which is an average of the base rotational speed
of the electric motor and a maximum rotational speed of the
electric motor, and the capacity coefficient of the torque
converter is such that the characteristic line for the torque
converter intersects the characteristic line for the electric motor
in the first range.
2. The power transmission device for a vehicle according to claim
1, wherein a second range corresponds to a range that is equal to
and greater than the base rotational speed of the electric motor
and is equal to or less than a second average rotational speed,
which is an average of the base rotational speed of the electric
motor and the first average rotational speed of the electric motor,
and the capacity coefficient of the torque converter is such that
the characteristic line for the torque converter intersects the
characteristic line for the electric motor in the second range.
3. The power transmission device for a vehicle according to claim
1, wherein the capacity coefficient is a capacity coefficient in an
instance where a speed ratio of the torque converter is zero.
4. The power transmission device for a vehicle according to claim
1, wherein the electric motor has a stator, and a rotor that has a
permanent magnet and that is configured to be capable of rotating
relative to the stator.
5. The power transmission device for a vehicle according to claim
1, wherein the base rotational speed is equal to and greater than
1500 (r/min) and is equal to and less than 3000 (r/min).
6. The power transmission device for a vehicle according to claim
5, wherein the base rotational speed is equal to and greater than
2000 (r/min) and is equal to and less than 2500 (r/min).
7. The power transmission device for a vehicle according to claim
5, wherein the characteristic line for the torque converter is set
based on the base rotational speed.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2018-148812 filed Aug. 7, 2018 and Japanese Patent
Application No. 2019-087750 filed May 7, 2019. The contents of
those applications are incorporated by reference herein in their
entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to a power transmission
device for a vehicle.
BACKGROUND ART
[0003] Conventional power transmission devices for vehicles are
provided with a motor generator (electric motor) and a torque
converter (see Japanese Laid-open Patent Application Publication
No. 2011-231857). In this configuration, drive force of the motor
generator is transmitted to an output shaft via the torque
converter.
BRIEF SUMMARY
[0004] Generally, in a conventional power transmission device for a
vehicle, a capacity coefficient YJ of a torque converter is set so
that a characteristic line TLJ for the torque converter intersects
a characteristic line ML for an electric motor in a range RL which
is less than a base rotational speed, the characteristic line ML
indicating a maximum output torque of a motor generator relative to
each rotational speed of the motor generator, as shown in FIG.
4.
[0005] This is because a maximum output torque Tm of the motor
generator in the range RL can be utilized by setting the capacity
coefficient YJ of the torque converter so that the characteristic
line TLJ for the torque converter intersects the characteristic
line ML for the electric motor in the range RL.
[0006] However, there is a risk that the capacity coefficient YJ of
the torque converter, e.g., the size (representative diameter
.phi.J) of the torque converter, will increase in order to cause
the characteristic line TLJ for the torque converter to intersect
the characteristic line ML for the electric motor. In this case,
the characteristic line TLJ for the torque converter passes through
a low-efficiency region in an efficiency map of the motor generator
as shown in FIG. 4, and a problem is therefore encountered in that
the motor generator cannot be efficiently utilized.
[0007] The present disclosure was devised in view of the problem
described above, and an object of the present disclosure is to
provide a power transmission device for a vehicle in which the
torque converter can be reduced in size. A further object of the
present disclosure is to provide a power transmission device for a
vehicle in which an electric motor can be efficiently utilized.
[0008] A power transmission device for a vehicle according to a
first aspect of the present disclosure comprises an electric motor
and a torque converter. The torque converter is connected to the
electric motor and transmits torque of the electric motor to an
output member.
[0009] In this aspect, a characteristic line for the torque
converter is determined on the basis of a capacity coefficient of
the torque converter. The characteristic line for the torque
converter indicates torque of the torque converter relative to each
rotational speed of the torque converter. A characteristic line for
the electric motor indicates a maximum output torque of the
electric motor relative to each rotational speed of the electric
motor.
[0010] A first range corresponds to a range that is equal to and
greater than a base rotational speed of the electric motor and is
equal to or less than a first average rotational speed, which is an
average of the base rotational speed of the electric motor and a
maximum rotational speed of the electric motor. The torque
converter includes a capacity coefficient such that the
characteristic line for the torque converter intersects the
characteristic line for the electric motor in the first range.
[0011] In the present power transmission device for a vehicle, the
first range corresponds to a range that is equal to and greater
than the base rotational speed of the electric motor and is equal
to or less than the first average rotational speed. Specifically,
the first range is greater than a range which is less than the base
rotational speed and is equal to or less than the first average
rotational speed. Additionally, the maximum output torque of the
first range defined by the characteristic line for the electric
motor is equal to and less than the maximum output torque in a
low-rotational-speed range (0.ltoreq.rotational speed.ltoreq.base
rotational speed) defined by the characteristic line for the
electric motor.
[0012] Comparing a first scenario in which the characteristic line
for the torque converter intersects the characteristic line for the
electric motor in the first range, and a second scenario
(conventional scenario) in which the characteristic line for the
torque converter intersects the characteristic line for the
electric motor in the range which is less than the base rotational
speed, the capacity coefficient of the first scenario is less than
one of the second scenario.
[0013] By causing the characteristic line for the torque converter
to intersect the characteristic line for the electric motor in the
first range in this manner, the capacity coefficient of the torque
converter can be made less than the capacity coefficient of a
conventional torque converter. Specifically, the torque converter
can be reduced in size. Additionally, by configuring the power
transmission device as described above, the electric motor can be
efficiently utilized because the characteristic line for the torque
converter can pass through a high-efficiency region of the electric
motor.
[0014] A power transmission device for a vehicle according to
another aspect of the present disclosure is preferably configured
in the following manner. A second range corresponds to a range that
is equal to and greater than the base rotational speed of the
electric motor and is equal to or less than a second average
rotational speed, which is an average of the base rotational speed
of the electric motor and the first average rotational speed of the
electric motor. The torque converter includes a capacity
coefficient such that the characteristic line for the torque
converter intersects the characteristic line for the electric motor
in the second range.
[0015] In this configuration, the second range corresponds to a
range that is equal to and greater than the base rotational speed
of the electric motor and is equal to or less than the second
average rotational speed. Specifically, the second range is greater
than the range which is less than the base rotational speed, and is
equal to or less than the second average rotational speed.
[0016] By causing the characteristic line for the torque converter
to intersect the characteristic line for the electric motor in the
second range, the capacity coefficient of the torque converter can
be made less than the capacity coefficient of a conventional torque
converter. Specifically, the torque converter can be reduced in
size. Additionally, by configuring the power transmission device as
described above, the electric motor can be efficiently utilized
because the characteristic line for the torque converter can pass
through a high-efficiency region of the electric motor.
[0017] In a power transmission device for a vehicle according to
another aspect of the present disclosure, the capacity coefficient
is preferably a capacity coefficient in an instance where a speed
ratio of the torque converter is zero. Even with this
configuration, the electric motor can be efficiently utilized
because the characteristic line for the torque converter can pass
through the high-efficiency region of the electric motor.
[0018] In a power transmission device for a vehicle according to
another aspect of the present disclosure, it is preferable that the
electric motor has a stator, and a rotor that has a permanent
magnet and is configured to be capable of rotating relative to the
stator.
[0019] Due to this configuration, at least part of the
high-efficiency region of the electric motor is formed in the
above-described first region or the above-described second region,
and the characteristic line for the torque converter can therefore
reliably pass through the high-efficiency region of the electric
motor. The electric motor can thereby be efficiently utilized.
[0020] In a power transmission device for a vehicle according to
another aspect of the present disclosure, it is preferable that the
base rotational speed is equal to and greater than 1500 (r/min) and
is equal to and less than 3000 (r/min). Thereby, the torque
converter can be suitably reduced in size.
[0021] In a power transmission device for a vehicle according to
another aspect of the present disclosure, it is preferable that the
base rotational speed is equal to and greater than 2000 (r/min) and
is equal to and less than 2500 (r/min). Thereby, the torque
converter can be suitably reduced in size.
[0022] In a power transmission device for a vehicle according to
another aspect of the present disclosure, it is preferable that the
characteristic line for the torque converter is set based on the
base rotational speed. Thereby, the torque converter can be
suitably matched to the electric motor. In other words, the torque
converter can be reduced in size.
[0023] In the power transmission device for a vehicle of present
disclosure, the torque converter can be reduced in size and the
electric motor can be efficiently utilized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic view showing an overall configuration
of a vehicle according to the present embodiment;
[0025] FIG. 2 is a cross-sectional view of a power transmission
device of the present embodiment;
[0026] FIG. 3A is a graph showing a characteristic of a motor and a
characteristic of a torque converter in the power transmission
device of the present embodiment;
[0027] FIG. 3B is a graph showing a characteristic of the motor and
a characteristic of the torque converter in the power transmission
device of the present embodiment; and
[0028] FIG. 4 is a graph showing characteristics of motors and
characteristics of torque converters in power transmission devices
of the present embodiment and of the prior art.
DETAILED DESCRIPTION
[0029] <Overall Summary>
[0030] FIG. 1 is a schematic view showing an overall configuration
of a vehicle in which a power transmission device 1 of the present
disclosure is disposed. A configuration relating to the power
transmission device 1 is described in a simple manner using FIG.
1.
[0031] Disposed in the vehicle are, for example, the power
transmission device 1, a control unit 2, and a battery unit 3, as
shown in FIG. 1. In this embodiment, an example is shown of a case
in which the control unit 2 and the battery unit 3 are not included
in the power transmission device 1, but the control unit 2 and/or
the battery unit 3 can be included in the power transmission device
1.
[0032] The power transmission device 1 is for driving drive wheels
4. The power transmission device 1 is installed in a vehicle body
(not shown). The power transmission device 1 is actuated by
electric power from the battery unit 3, and drives the drive wheels
4 via a first output shaft 5 (one example of an output member) and
a second output shaft 6. A first gear part 7 is provided to the
first output shaft 5. A second gear part 8 is provided to the
second output shaft 6. The second gear part 8 meshes with the first
gear part 7. A differential mechanism 9 is disposed between the
second output shaft 6 and the drive wheels 4.
[0033] With this configuration, when drive force is transmitted
from the power transmission device 1 to the first output shaft 5,
the drive force is transmitted from the second output shaft 6 to
the drive wheels 4 via the differential mechanism 9. Thus, the
drive wheels 4 are driven by the power transmission device 1.
[0034] The term "drive force" includes torque. A power transmission
path described above is one example, and the drive force of the
power transmission device 1 can be transmitted to the drive wheels
4 using another output shaft and/or gear part as well. The details
of the power transmission device 1 are described hereinafter.
[0035] The control unit 2 controls the power transmission device 1
and the battery unit 3. The control unit 2 is installed in the
vehicle body. The control unit 2 is actuated by electric power from
the battery unit 3.
[0036] The battery unit 3 supplies electric power to the power
transmission device 1 and the control unit 2. The battery unit 3 is
installed in the vehicle body. The battery unit 3 can be charged by
an external power source. The battery unit 3 can also be charged
using electric power generated in the power transmission device
1.
[0037] <Power Transmission Device>
[0038] The power transmission device 1 is for transmitting drive
force to the first output shaft 5. The power transmission device 1
is provided with a motor 13 (one example of an electric motor) and
a torque converter 15, as shown in FIG. 2. Specifically, the power
transmission device 1 is provided with a casing 10, the motor 13,
and the torque converter 15. The power transmission device 1 is
further provided with a rotation transmission structure 17. The
power transmission device 1 is further provided with a lock-up
structure 19. The casing 10 is attached to the vehicle body. The
casing 10 has an internal space S.
[0039] (Motor)
[0040] The motor 13 is a drive part of the power transmission
device 1. The motor 13 is disposed in the internal space S of the
casing 10, as shown in FIG. 2. The motor 13 has a first stator 21
(one example of a stator) and a rotor 22. The first stator 21 is
secured to the casing 10. A coil part 21a is provided to the first
stator 21.
[0041] The rotor 22 is configured to be capable of rotating
relative to the first stator 21. The rotor 22 is supported to be
capable of rotating relative to the first output shaft 5.
Specifically, the rotor 22 is supported through the rotation
transmission structure 17 to be capable of rotating relative to the
first output shaft 5.
[0042] The rotor 22 is positioned along an axial direction by a
positioning member 34. The positioning member 34 is attached to the
rotor 22 so as to be capable of rotating integrally with the rotor
22, and is supported on the first output shaft 5 so as to be
capable of rotating relative to the first output shaft 5.
[0043] The rotor 22 has a permanent magnet. Specifically, the rotor
22 is provided with a magnet part 22a in which an N pole and an S
pole are alternatingly disposed in a circumferential direction. The
magnet part 22a is configured from a permanent magnet.
[0044] A current is supplied to the coil part 21a of the first
stator 21 from the battery unit 3 (see FIG. 1), and when a magnetic
field is generated between the coil part 21a and the magnet part
22a, the rotor 22 rotates relative to the first stator 21 about a
rotational axis of the first output shaft 5. The current from the
battery unit 3 is controlled by the control unit, whereby the
rotation of the rotor 22 is controlled.
[0045] In the present embodiment, the motor 13 functions as a
permanent magnet synchronous motor because the magnet part 22a
having a permanent magnet is included in the rotor 22. Due to the
motor 13 being configured in this manner, the motor 13 forms an
efficiency map (see FIGS. 3A and 3B described hereinafter) having,
for example, high-efficiency regions E1, E2 (see FIG. 4, described
hereinafter) in the center.
[0046] (Torque Converter)
[0047] The torque converter 15 is connected to the motor 13. The
torque converter 15 transmits drive force of the motor 13 to the
first output shaft 5. Specifically, the torque converter 15
transmits the rotation of the rotor 22 to the first output shaft 5
when the rotor 22 rotates in a drive direction R1 (see FIG. 1). The
drive direction R1 is a direction in which the rotor 22 is caused
to rotate in order to move the vehicle forward.
[0048] The torque converter 15 is disposed inside the casing 10,
i.e., in the internal space S of the casing 10, as shown in FIG. 2.
The torque converter 15 has an impeller 25, a turbine 27, and a
second stator 29. The torque converter 15 causes the impeller 25,
the turbine 27, and the second stator 29 to rotate via hydraulic
oil, whereby torque inputted to the impeller 25 is transmitted to
the turbine 27.
[0049] The impeller 25 is configured to be capable of rotating
integrally with the rotor 22. For example, the impeller 25, e.g.,
an impeller shell 25a, is secured to a cover part 32. A torque
converter case is formed by the impeller shell 25a and the cover
part 32 secured to the rotor 22. The torque converter case is a
non-magnetic body.
[0050] The turbine 27 is linked to the first output shaft 5. The
turbine 27 is linked to be capable of rotating integrally with the
first output shaft 5. A turbine shell 27a of the turbine 27 is
disposed between the impeller shell 25a and the cover part 32. The
second stator 29 is configured to be capable of rotating relative
to the casing 10. For example, the second stator 29 is disposed to
be capable of rotating relative to the casing 10 by means of a
one-way clutch 30.
[0051] (Rotation Transmission Structure)
[0052] The rotation transmission structure 17 selectively transmits
the rotation of the rotor 22 to the first output shaft 5. The
rotation transmission structure 17 is disposed in the internal
space S of the casing 10, between the rotor 22 and the first output
shaft 5, as shown in FIG. 2. For example, the rotation transmission
structure 17 has a one-way clutch 17a.
[0053] For example, when the rotor 22 rotates in the drive
direction R1, the one-way clutch 17a does not transmit the rotation
of the rotor 22 to the first output shaft 5. Conversely, when the
rotor 22 rotates in a counter-drive direction R2 (see FIG. 1), the
one-way clutch 17a transmits the rotation of the rotor 22 to the
first output shaft 5. The counter-drive direction R2 is a
rotational direction opposite from the drive direction R1.
[0054] (Lock-Up Structure)
[0055] The lock-up structure 19 is disposed in the internal space S
of the casing 10. The lock-up structure 19 links the impeller 25
and the turbine 27 so as to enable integrated rotation
therebetween.
[0056] The lock-up structure 19 has a centrifugal clutch 31, as
shown in FIG. 2. A centrifugal element 31a of the centrifugal
clutch 31 is provided to the turbine 27, e.g., to the turbine shell
27a. Specifically, a plurality of centrifugal elements 31a
configuring the centrifugal clutch 31 are disposed at intervals
along the circumferential direction (rotational direction), and are
held on the turbine shell 27a so as to be capable of moving
radially relative to the turbine shell 27a and capable of rotating
integrally with the turbine shell 27a.
[0057] The plurality of centrifugal elements 31a are disposed
facing a radially outward side part 25b of the impeller shell 25a.
A friction member 31b is provided to each of the plurality of
centrifugal elements 31a. The friction members 31b of the
centrifugal elements 31a are disposed at intervals away from the
radially outward side part 25b of the impeller shell 25a.
[0058] Specifically, when centrifugal force is not acting on the
plurality of centrifugal elements 31a, or when centrifugal force
acting on the plurality of centrifugal elements 31a is less than a
predetermined centrifugal force, the plurality of centrifugal
elements 31a (the friction members 31b) are disposed at intervals
away from the radially outward side part 25b of the impeller shell
25a. This state is a clutch OFF state.
[0059] Conversely, a state in which the friction members 31b of the
centrifugal elements 31a are in contact with the radially outward
side part 25b of the impeller shell 25a is a clutch ON state.
Specifically, when the centrifugal force acting on the plurality of
centrifugal elements 31a is equal to or greater than the
predetermined centrifugal force, the plurality of centrifugal
elements 31a (the friction members 31b) come into contact with the
radially outward side part 25b of the impeller shell 25a. The
impeller 25 and the turbine 27 are thereby linked so as to be
capable of rotating integrally. This state is the clutch ON
state.
[0060] <Characteristics of Motor and Torque Converter>
[0061] FIGS. 3A and 3B are graphs showing characteristics of the
motor 13 and the torque converter 15, in which the horizontal axis
represents rotational speed V (r/min) and the vertical axis
represents torque T (Nm).
[0062] (Characteristic for Motor)
[0063] The solid lines in FIGS. 3A and 3B indicate a characteristic
line ML for the motor when the motor 13 is actuated alone, as well
as indicating a relationship between rotational speed V and output
torque T in the motor 13. Specifically, the solid lines indicate a
characteristic line ML for the motor when the motor 13 is actuated
alone, as well as indicating the output torque T relative to each
rotational speed V in the motor 13. The phrase "when the motor 13
is actuated alone" includes the meaning of "when the motor 13 is
actuated alone without increasing or reducing speed."
[0064] In the characteristic line ML for the motor, a maximum
output torque Tm of the motor 13 is kept substantially constant by
limiting current in the low-rotational-speed range, e.g., a range
in which the rotational speed V is equal to and greater than 0 and
is equal to and less than a base rotational speed Na
(0.ltoreq.rotational speed.ltoreq.base rotational speed Na).
[0065] On the other hand, in the characteristic line ML for the
motor, at a rotational speed range RM having a rotational speed V
greater than the base rotational speed Na of the
low-rotational-speed range RL (base rotational speed
Na<rotational speed V<maximum rotational speed Nm), the
current flowing to the coil part 21a of the first stator 21 is
reduced by a counter electromotive voltage as the rotational speed
V of the motor 13 increases. Therefore, the maximum output torque T
(T<Tm) of the motor 13 decreases.
[0066] The efficiency map of the motor 13 indicates a distribution
of the efficiency of the motor 13, as shown in FIG. 4. The
efficiency of the motor 13 is defined by a ratio of mechanical
output (W) from the motor 13 to input electric power (W) inputted
to the motor 13.
[0067] For example, the efficiency of the motor 13 is expressed as
follows:
motor efficiency=[mechanical output (W)/input electric power
(W)].times.100(%)
[0068] The input electric power is expressed as follows:
input electric power (W)=voltage (V).times.current (A)
[0069] The mechanical output is expressed as follows:
mechanical output (W)=rotational speed (r/min).times.torque
(Nm)
[0070] (Characteristic for Torque Converter)
[0071] The single-dash lines in FIGS. 3A and 3B indicate a
characteristic line TL for the torque converter 15, as well as
indicating a relationship between rotational speed V and torque T
in the torque converter 15. Specifically, the single-dash lines
correspond to a capacity coefficient Y (Y1 and Y2, described
hereinafter) in the torque converter 15.
[0072] The input rotational speed V of the torque converter 15 is a
rotational speed inputted from the motor 13 to the torque converter
15. The input torque T of the torque converter 15 is the torque
inputted from the motor 13 to the torque converter 15.
[0073] The characteristic line TL (TL1 and TL2, described
hereinafter) for the torque converter 15 is determined on the basis
of the capacity coefficient Y. For example, in the characteristic
line TL for the torque converter 15, the torque T is proportional
to the square of the rotational speed V. The capacity coefficient Y
is a proportionality coefficient. Specifically, the characteristic
line TL for the torque converter 15 is expressed by
"T=Y.times.(V.sup.2)." The characteristic line TL for the torque
converter 15 thereby draws nearer to the vertical axis as the
capacity coefficient Y increases, and draws away from the vertical
axis as the capacity coefficient Y decreases.
[0074] The size, e.g., the representative diameter co of the torque
converter 15 is defined on the basis of the capacity coefficient Y.
The representative diameter .phi. is an outside diameter of a torus
(a fluid operation chamber). For example, the capacity coefficient
Y is proportional to the fifth power of the size, e.g., the
representative diameter .phi. of the torque converter 15.
Specifically, the capacity coefficient Y is expressed as
Y=A.times.(.phi..sup.5). In this equation, A is a proportionality
coefficient and is set to a predetermined value. The capacity
coefficient Y thereby decreases when the representative diameter
.phi. of the torque converter 15 decreases. In other words, when
the capacity coefficient Y decreases, the representative diameter
.phi. of the torque converter 15 decreases.
[0075] To summarize what is described above, the representative
diameter .phi. of the torque converter 15 decreases as the capacity
coefficient Y decreases. Additionally, when the capacity
coefficient Y, e.g., the representative diameter .phi. of the
torque converter 15, decreases, the characteristic line TL for the
torque converter 15 draws away from the vertical axis.
[0076] (Relationship of Motor and Torque Converter)
[0077] In the characteristic graph shown in FIG. 3A, the capacity
coefficient Y1 of the torque converter 15 is such that the
characteristic line TL1 for the torque converter 15 intersects the
characteristic line ML for the motor in a first range RA. The
capacity coefficient Y1 is preferably a capacity coefficient in
where a speed ratio of the torque converter 15 is zero. The speed
ratio is defined by, for example, a ratio of a rotational speed of
the turbine 27 to a rotational speed of the impeller 25.
Hereinafter, the intersection point of the characteristic line TL1
for the torque converter 15 and the characteristic line ML for the
motor is indicated by a black circle.
[0078] The first range RA corresponds to a range equal to and
greater than the base rotational speed Na of the motor 13, and
equal to or less than a first average rotational speed N1. The
first average rotational speed N1 is determined by an average of
the base rotational speed Na of the motor 13 and the maximum
rotational speed Nm of the motor 13. The base rotational speed Na
of the motor 13 is a speed at which a switch is made from a state
in which torque is constant to a state in which the mechanical
output described above is constant.
[0079] The characteristic line TL1 for the torque converter 15 is
determined on the basis of the capacity coefficient Y1.
Specifically, the capacity coefficient Y1, e.g., a representative
diameter .phi.1 of the torque converter 15, is established such
that the characteristic line TL1 for the torque converter 15
intersects the characteristic line ML for the motor in the first
range RA.
[0080] Due to this configuration, in a case in which the
characteristic line TL1 for the torque converter 15 intersects the
characteristic line ML for the motor in the first range RA (see
FIG. 3A), the characteristic line TL1 for the torque converter 15
draws farther away from the vertical axis than in a case in which
the characteristic line TLJ for the torque converter 15 intersects
the characteristic line ML for the motor in the range RL which is
less than the base rotational speed Na (see FIG. 4) as in the prior
art.
[0081] Specifically, in a case in which the characteristic line TL1
for the torque converter 15 intersects the characteristic line ML
for the motor in the first range RA (see FIG. 3A), the
characteristic line TL2 for the torque converter 15 draws farther
away from the vertical axis than in a case in which the
characteristic line TLJ for the torque converter 15 intersects the
characteristic line ML for the motor in the range RL which is less
than the base rotational speed (see FIG. 4) as in the prior
art.
[0082] In this case, the capacity coefficient Y1 is less than the
capacity coefficient YJ of the prior art. Specifically, the
representative diameter .phi.1 is less than a representative
diameter .phi.J of the prior art. Thus, in the present power
transmission device 1, the torque converter 15 can be reduced in
size.
[0083] The torque converter 15 can have a capacity coefficient Y2
such that the characteristic line TL2 for the torque converter 15
intersects the characteristic line ML for the motor in a second
range RB, as shown in FIG. 3B. The capacity coefficient Y2 is
preferably a capacity coefficient in a case in which the speed
ratio of the torque converter 15 is zero.
[0084] The second range RB corresponds to a range equal to and
greater than the base rotational speed Na of the motor 13, and
equal to or less than a second average rotational speed N2. The
second average rotational speed N2 is determined by an average of
the base rotational speed Na of the motor 13 and the first average
rotational speed N1 of the motor 13.
[0085] The characteristic line TL2 for the torque converter 15 is
determined on the basis of the capacity coefficient Y2.
Specifically, the capacity coefficient Y2, e.g., a representative
diameter .phi.2 of the torque converter 15, is established so that
the characteristic line TL2 for the torque converter 15 intersects
the characteristic line ML for the motor in the second range
RB.
[0086] Due to this configuration, in a case in which the
characteristic line TL2 for the torque converter 15 intersects the
characteristic line ML for the motor in the second range RB (see
FIG. 3B), the characteristic line TL2 for the torque converter 15
draws farther away from the vertical axis than in a case in which
the characteristic line TLJ for the torque converter 15 intersects
the characteristic line ML for the motor in the range RL which is
less than the base rotational speed (see FIG. 4), as in the prior
art.
[0087] In this case, the capacity coefficient Y2 is less than the
capacity coefficient YJ of the prior art. Specifically, the
representative diameter .phi.2 is less than the representative
diameter .phi.J of the prior art. Even with this configuration, in
the present power transmission device 1, the torque converter 15
can be reduced in size.
[0088] Whether to use the torque converter 15 having the
characteristic line TL1 (capacity coefficient Y1 and representative
diameter .phi.1) shown in FIG. 3A or the torque converter 15 having
the characteristic line TL2 (capacity coefficient Y2 and
representative diameter .phi.2) shown in FIG. 3B as the torque
converter 15 is preferably selected in accordance with the
efficiency map of the motor 13.
[0089] When the characteristic lines TL1, TL2 for the torque
converter 15 are caused to intersect the characteristic line ML for
the motor as in FIGS. 3A and 3B, the characteristic lines TL1, TL2
for the torque converter 15 pass through a first region E1 in the
efficiency map of the motor 13.
[0090] Specifically, in a state in which the characteristic lines
TL1, TL2 for the torque converter 15 respectively intersect the
characteristic line ML for the motor in the first range RA or the
second range RB, the characteristic lines pass through the first
region E1 and a second region E2 in the efficiency map of the motor
13.
[0091] In this embodiment, the first region E1 indicates a region
in which, for example, the efficiency of the motor 13 is 85% or
greater in the efficiency map of the motor 13. The second region E2
indicates a region in which the efficiency of the motor 13 is 90%
or greater in the efficiency map of the motor 13.
[0092] Specifically, the torque converter 15 has the capacity
coefficients Y1, Y2 such that the characteristic lines TL1, TL2 for
the torque converter 15 respectively pass through the first region
E1 (a region of 85%) of the efficiency map of the motor 13, or the
first region E1 (a region of 85%) and the second region E2 (a
region of 90%) of the efficiency map.
[0093] Thus, the motor 13 can be efficiently utilized by causing
the characteristic line TL for the torque converter 15 to pass
through high-efficiency regions E1, E2 (the first region E1 and/or
the second region E2) in the efficiency map of the motor 13.
Specifically, torque can be efficiently outputted from the power
transmission device 1 to the first output shaft 5.
[0094] In this embodiment, the capacity coefficient of the torque
converter 15 is preferably 5 to 30.times.10.sup.-6
(Nm/(r/min).sup.2). It is possible to efficiently utilize the motor
13 while reducing the torque converter 15 in size by configuring
the motor 13 and the torque converter 15 using the torque converter
15 having such characteristics. Specifically, torque can be
efficiently outputted from the power transmission device 1 to the
first output shaft 5 while reducing the torque converter 15 in
size.
Other Embodiments
[0095] The previous embodiment is not provided by way of limitation
to the present disclosure; various modifications or revisions can
be made without deviating from the scope of the present
disclosure.
[0096] (A) The configuration of the previous embodiment is not
provided by way of limitation to the configuration of the power
transmission device 1, which can be configured in any manner as
long as the torque and rotation of the motor 13 can be transmitted
to the torque converter 15.
[0097] (B) In the previous embodiment, an example was presented of
a case in which the rotation transmission structure 17 selectively
transmits the rotation of the rotor 22 to the first output shaft 5.
In a case in which this rotation transmission structure 17 is
replaced by a rotation support structure and the rotor 22 rotates
in the drive direction R1 or the counter-drive direction R2, the
rotation of the rotor 22 can be transmitted to the first output
shaft 5 via the torque converter 15.
[0098] (C) In the previous embodiment, an example was presented of
a case in which the lock-up structure 19 has the centrifugal clutch
31, but the lock-up structure 19 can be configured in any manner as
long as the impeller 25 and the turbine 27 can be linked to be
capable of rotating integrally.
[0099] (D) In the previous embodiment, an example was presented of
a case in which the characteristic lines TL1, TL2 for the torque
converter 15 pass through both the first region E1 and the second
region E2 in the efficiency map of the motor 13, but the capacity
coefficients Y1, Y2 are preferably established so that the
characteristic lines TL1, TL2 for the torque converter 15 pass
through at least the first region E1 (a region of 85%).
[0100] (E) In the previous embodiment, as shown in FIG. 3A, FIG.
3B, and FIG. 4, the characteristic line TL3 of the torque converter
15 is set based on the base rotational speed Na of the motor 13.
For example, the characteristic line TL3 of the torque converter 15
intersects the characteristic line ML of the motor 13 on the base
rotational speed Na of the motor 13 (or near the base rotational
speed Na of the motor 13).
[0101] In this case, the base rotational speed Na is set in a
predetermined range DNa. For example, it is preferable that the
predetermined range DNa is equal to and greater than 1500 (r/min)
and is equal to and less than 3000 (r/min). Specifically, it is
preferable that the predetermined range DNa is equal to and greater
than 2000 (r/min) and is equal to and less than 2500 (r/min).
[0102] The motor 13 is selected such that the base rotational speed
Na is included in the predetermined range DNa. In case that the
motor 13 is selected such that the base rotational speed Na is not
included in the predetermined range DNa, the motor 13 is adjusted
such that the base rotational speed Na is included in the
predetermined range DNa.
[0103] The characteristic line TL3 of the torque converter 15 is
set based on the base rotational speed Na of this motor 13 (or a
value near the base rotational speed Na of this motor 13). In other
words, the torque converter 15 can be suitably matched to the motor
13 by providing the torque converter 15 including the
characteristic line TL3 respect to the motor 13 including the above
base rotational speed Na. In other words, the torque converter 15
can be reduced in size.
REFERENCE SIGNS LIST
[0104] 1 Power transmission device [0105] 13 Motor [0106] 15 Torque
converter [0107] 21 First stator [0108] 22 Rotor [0109] TL1, TL2
Characteristic lines for torque converter [0110] TLJ Characteristic
line for conventional torque converter [0111] ML Characteristic
line ML for electric motor [0112] RA First range [0113] RB Second
range [0114] E1 First region [0115] E2 Second region [0116] Y1, Y2
Capacity coefficients [0117] YJ Conventional capacity coefficient
[0118] .phi.1, .phi.2 Representative diameter [0119] .phi.J
Conventional representative diameter
* * * * *